1. Field of the Invention
The present invention relates to an optical projection system, and more particularly to an optical projection system that is thin, light and capable of controlling a distortion of an image projected by the optical projection system.
2. Description of the Related Art
An optical projection system generally includes a light source capable of generating a light beam, a parabola reflector capable of reflecting the light beam, an illumination lens capable of compressing the light beam, a light valve capable of converting the light beam into an image in response to an electrical image signal, an optical projection lens capable of magnifying and projecting the image and a screen capable of displaying the image.
A basic working principle of the optical projection system is as follows. First, the light source generates a light beam. The light beam is reflected by the parabola reflector and projected on the illumination lens, which further projects the light beam onto the light valve. The light valve converts the light beam into an image in response to an electrical image signal and projects the image to the optical projection lens. The optical projection lens magnifies the image and projects the magnified image to the screen so as to display the magnified image thereon.
However, for the optical projection system as mentioned above, the overall thickness of the system depends on the distance between the parabola reflector and the screen. Wide angle optical projection lenses capable of projecting images in a wide angle have been used to reduce the overall thickness of the optical projection system, but the wide angle optical projection lenses are limited in the view angles they provide. To overcome this problem, U.S. Pat. No. 4,003,080 discloses an optical projection system 10 as shown in FIG. 1. A curved reflecting element having a convex curvature 14 and a planar reflecting element 16 are used to reflect a light beam coming from an optical projection lens 12, and change the optical path of the light beam so as to project the light beam onto a screen 18 in compact space. An overall volume of the optical projection system is thus reduced. In addition, U.S. Pat. No. 6,406,150 discloses a rear projection system 20 as shown in FIG. 2, in which a curved cylindrical reflecting element 24 is configured to change an optical path of a light beam coming from an optical projection lens 22 so as to project the light beam onto a screen 26 while reducing an overall volume of the rear projection system 20. Although the overall volumes of the optical projection systems as mentioned above are reduced, the issue of image distortion after the light beam being reflected or refracted is not considered so that the resulted images generally carry trapezoidal distortion, which may severely degrade the resulted image quality. Hence it is desired to provide an optical projection system that overcomes the above-mentioned image distortion problem.
Other objectives, features and advantages of the present invention will be further understood from the further technological features disclosed by the embodiments of the present invention wherein there are shown and described preferred embodiments of this invention, simply by way of illustration of modes best suited to carry out the invention.